Could I work out sensor size of my phone from these info: F-stop= f/2.6 , focal length = 3mm, max aperture = 2.8 and others info like: resolution unit, exposure time?
(I think - see below)
F-Stop and Aperture (these two are in fact the same thing) is/are a property of the lens.
Focal Length - again, a property of the lens.
Resolution Unit - I dunno exactly what you mean but most probably you mean „how many (mega)pixels are on the sensor”. „Sensor Size” is different from this because Sensor Size means how many millimeters (or any other appropriate length unit) and NOT how many pixels has the sensor in Length x Height.
Exposure time - totally unrelated. It represents the time which the „hole” (aperture) is open. In other words how much time the sensor receives light.
In fact, (especially for phones) the manufacturer should say in the specs sheet the dimensions of the sensor. However for smartphone cameras this spec isn't so important because anyway the dimensions are very tiny.
If you actually know focal length accurately, and if you can measure the cameras field of view (the horizontal and vertical distance that it sees... at a certain distance, at least six feet), then see
Option 8 there will compute your sensor size.
Or if you know the crop factor for your camera (often in the specs), Option 3 there will compute it.
If you know these numbers, and want to compute distance to an object in the image, see http://scantips.com/lights/subjectdistance.html